The present invention concerns an indicator signalling the approach of the end of life of a battery operating a timepiece.
There is already in existence, for example on pocket calculators, an indicator showing the user that the operating battery voltage is becoming too low; this indication may be given by the simultaneous illumination of all the decimal points of the display system. In certain timepieces an indicator has been provided which emits a visible signal as long as the battery is in a good state; the signal ceases when the battery voltage becomes too low.
In the first case, the use of light-emitting diodes has the disadvantage that the battery, already becoming exhausted must furnish energy not only to the apparatus itself but also to the indicator system, which further shortens the life of the battery. In the second case it is clear that the length of life of the battery may be seriously reduced because the display indicating the state of the battery is visible during the whole of the duration of the life of the battery. There are also electronic devices adapted to detect the moment where the voltage of the battery falls below a predetermined limit. They are however used for relatively high voltages and do not lend themselves readily to use in wristwatches.